Takahashi FC-76 DCU Review

For many observers, there is something about a high quality refractor that no other telescope design can quite match. Clearly I buy into that line of thinking given the scopes that are displayed on the “My Equipment” page of this website. I have even been known to state (with tongue slightly in cheek) that “mirrors are for shaving.” However, and this comes from experience, larger aperture models become very unwieldy and difficult to mount, but at the smaller end of the aperture spectrum, four inches and under, they represent perhaps the best choice for grab and go scope and certainly as a travel scope to supplement a larger scope that stays at home.

In the 21st century, ever increasing urbanisation and the inevitable increase in light pollution that comes with it, means distant travel is becoming a necessary evil to find truly dark skies. That can mean international journeys and the restriction of airline baggage allowance. While I am happy to leave a tripod and mount in my checked luggage at the mercy of baggage-handlers, the fragile optical components need to ride with me in the cabin which introduces fairly severe restrictions on maximum dimensions and weight. Length of the OTA in particular eliminates a large number of potential refractors given the most generous airline cabin bag must be no more than 56cm long (22 inches). While my own APM TMB 105 triplet Apo (read the review here) at only 19” long comfortably complies, the scope is rather heavy at around 7kg with tube rings, finder and diagonal which means a more robust mounting solution must be taken along, something that is not always practical.

My annual trips to Africa which have very limited total baggage weight limits due to small aircraft used for internal flights left me looking for a high quality, light weight refractor for those times when a Cessna or helicopter was part of my travel itinerary.

The FC-76 Objective Unit screws in place of the FS-60 lens cell assembly, creating the 3″ f/7.5 FC-76.

The search initially led me to the Takahashi FS-60 (read the review of that scope here) which is less than 30cm in length and weighs little more than 1.3kg meaning I can always take optical aid on a trip, no matter how tight the luggage restrictions are. As fantastic a performer as that scope is, it is still only a 6cm (2.4”) aperture scope and can only do so much. However, one feature that really appealed about the basic FS-60 is its modular nature where a whole host of adaptors including extenders and flatteners can be screwed in changing the optical parameters of the system. The most exciting of which is the FC-76 Objective Unit which screws in place of the FS-60 lens assembly, converting the scope into a full 3” FC-76DC.

The Takahashi FC-76
Takahashi pioneered the use of artificially grown fluorite in telescope lenses with a number of early models hitting the marketplace in in the 1970s. The original f/8 FC-76 model was launched in 1981 and was discontinued many years later with the introduction of the FS series which placed the positive fluorite element at the front in a more traditional Fraunhofer configuration. More recently, Takahashi has reintroduced the FC series in 76mm and 100mm models, though these new versions have reduced the focal ratio to f/7.5.

The FC-76 is available in two models, the DS and DC. The DS model is larger with a 95mm diameter optical tube, sliding dew shield as well as a heavier duty 2.6” focuser from the Sky-90. The DS is 550mm long and weighs 3.0kg (6.6lbs). The DC model is a lighter weight (1.8kg / 3.9lbs), narrow body version (80mm) of the same objective lens design, coming with a smaller focuser that is also found on the FS-60. The dew shield on this model is fixed which increases the OTA length to 650mm. At 3kg the DS model is perhaps a little heavy to be called truly portable under any condition, and the DC model is a little too long to comply with international travel cabin baggage allowance. Fortunately, there is a third choice which combines the best of both the DS and DC. That is where the FC-76 Objective Unit comes in. The DC model shares the same optical tube diameter as the FS-60 which means the lens cell can simply be removed and the 76mm unit can be screwed in its place. Now you are faced with a 76mm scope that weighs less than 2kg, and thanks to the fact that it splits in two, no component is longer than 34cm resulting in compliance with the most restrictive of baggage dimension allowances.

Though I own the FS-60, each component required to create the FC-76 DCU is available separately so you can own the split tube FC-76 without purchasing the FS-60.

What if you do not want to pay for a FS-60 telescope as well? Fortuitously, you can put this scope together yourself. To do so, you would need a 2” Feathertouch focuser (I recommend the FTF2015BCR-LW) at around £430, the Starlight Instruments Takahashi Adaptor (part number A20-302) at £80, the FS-60CB tube (part number TSK06211) at £95, and the FC-76DC objective upgrade (TFK07650) which costs £931. The total price is around £1,500, compared to approximately £1,200 for the regular DC model, though you are benefiting from an upgraded focuser in the form of a Feathertouch and now have the advantage of a more portable scope.

The travel bag provided with the purchase of the FC-76 DCU when purchased in Japan. Source: takahashijapan.com

Takahashi themselves have now acknowledged the attractiveness of this split tube arrangement, announcing the FC-76 DCU in December 2016 with the components coming in a small travel bag. However, I have yet to see any sign of this model on any western Takahashi dealer site so if this seems attractive, you should speak with your local retailer.

The OTA
The first thing that strikes you about the FC-76 Objective Unit is actually how well packed it is. Tripled boxed with polystyrene inserts, plenty of bubble wrap and packing chips means there is no danger of the scope not arriving in perfect condition. As soon as you liberate the scope from the packaging, the quality is instant Takahashi. The OTA is wonderfully finished with a deep, pearly white paint with silver accent around the lens cell and capped with the classic “Takahashi Green” lens cover.

Takahashi offer two clamshells with an internal diameter of 80mm that can be used with the FC-76DC. The FS-60 clamshell is narrower with a small foot which offsets the mounting position which helps with balance of scope that can be slightly back heavy, despite its length, when using a large 2” eyepiece. The larger clamshell is actually intended for the FC-76DC but I find the smaller model more than capable and appreciate the reduced weight when travelling. Should clamshells not be your thing, the Borg (part number 7083) tube rings will also fit the scope.

The two 80mm inside diameter clamshells available for the FC-76 narrow body DC model.

The Lens
The FC-76 uses a doublet lens in a less common Steinheil arrangement with the positive fluorite element at the rear and a negative eco-glass element at the front. Amateur astronomers are known to fixate on the type of ED-glass used in a refractor lens, and while many have dispersive characteristics which come close to artificially grown crystalline fluorite (in reality it is the mating element which determines colour correction), for me at least, the most exciting property of fluorite is the reputation for scattering less light than any glass, a vital property for producing high contrast views which are crucial in astronomical observation. Having used the FS-60 for a number of years, the extreme contrast and low scatter demonstrated by that scope has left me a bit of a believer that the reputation is deserved.

The lens of the FC-76. Even with a point blank flash from the camera, the lack of reflection and scatter is obvious.

The lens sits in a wonderfully machined, temperature compensating cell, which is not much larger than the lens itself. To maintain the narrow diameter of the scope, there are no collimation screws on the 76DC (the FC-76DS can be user collimated) though I would highlight that over more than two years of use, I have removed the objective unit many times, and it has not lost collimation upon reattachment, thanks to the excellent machining and fine tolerance of the matching threads on the objective unit and secondary tube. Unlike the original FC series of scopes, all lens surfaces are fully multicoated and the quality of the broadband ant-reflection coatings are first class, only revealing themselves via slight reflections when a bright light shines directly on them.

The optics can show some minor astigmatism during cool down but this is completely absent once cooled and only seems to manifest when sudden extremes of temperature are encountered such as moving from a warm house out into a frigid winter night. Even then, patience does not need to be a virtue as the scope cools in a matter minutes and will then perform at its best.

The inside of both the Objective Unit and secondary tube are painted flat black with a couple of knife-edge baffles which help to minimise stray reflections from off-axis light rays.

If I have one criticism, it is the length of the dew shield beyond the front lens surface. With the diameter of the main tube barely larger than the lens itself, the lens cell actually sits inside the dew shield meaning it only extends a couple of inches beyond the lens and on particular damp nights, I have had some problems with the lens fogging up earlier perhaps than I would had the shield been a bit longer.

Focuser
What more can be written about Starlight Instruments Feathertouch focusers that has not been shared many times before? Almost universally believed to be the finest focusers available, they are wonderfully machined, precise and very strong. The lightweight model I use with both my FS-60 and the FC-76 is the FTF2015BCR-LW which has a 1.5” long drawtube. The lightweight model performs just as well as the regular two inch feathertouch focuser (which I have on both of my 4” class APM LZOS triplets) but weighs 0.278lbs less at 0.848lbs. I would also highlight, that aesthetically at least, the silver skeleton cage of the lightweight model is an excellent match for the silver accent around the lens cell assembly of the FC-76.

The stock Takashashi focuser supplied with the FS-60 and FC-76 only has 1″ of travel as seen here fully extended.

The standard equipment Takahashi focuser that comes with the FS-60 and FC-76DC is a single speed unit which is very smooth, but perhaps lacks the absolute precision of a Feathertouch focuser. Natively, the focuser will not accept 2” accessories though an adaptor is available. However, the biggest weakness is the drawtube is only one inch in length. The consequence of this is that a visual observer will find themselves screwing in and removing adaptors as a means of course focus with final fine adjustments coming from the focuser itself. As someone who often finds themselves switching eyepieces rather frequently, this can be a bit of pain. Barlow lenses which are not usually par-focal can shift the focus point of an eyepiece considerably so consider a Tele Vue Powermate or better yet, a Nagler Zoom for high power viewing. It is worthy of note that there is some minor evidence of cost cutting as the focus wheels are painted plastic as opposed to metal found on the larger Tak focusers.

6×30 Finder
As the FC-76 is rather portable, it has accompanied me to many of the monthly Baker Street Irregular star parties in central London. While most attendees are more than happy for a quick peak at whatever celestial delight the scope is currently pointed at, occasionally someone comes along who is in the market for a small refractor and starts asking plenty of questions. Almost always they know what the scope is, and if it is a potential option, it usually means they are relatively experienced astronomers (at its price point it is hardly an entry level model). More often than not, at some point that questioning turns to the cute little finder and whether it is “worth the money?” or “surely a 50mm finder would be better?” That is when I tell them to look through it.

The wonderful 6×30 Takahashi finder and bracket mounted on a 76mm tube-ring for attachment to the scope.

The almost ubiquitous 50mm finder seems to have been rapidly declining in quality over the last few years. The images are dull, only vaguely sharp in the middle of the field, while offering limited eye relief. The 6x30mm (8o field) Takahashi finder is somewhat of a minor legend because it has none of those qualities. The images are bright and crisp across almost the entire field and it is delivered with copious amounts of eye relief. Everyone who looks through it is impressed and it certainly leaves them giving serious consideration to spending the £130 asking price for the finder and bracket.

The build quality matches the high quality of the Takahashi line of scopes with the same excellent optical coatings and wonderful deep white paint finish. In my opinion it is the finest finder I have ever used.

However, if you have built your split tube FC-76 from scratch, or just switched out the stock focuser of your FS-60 for a sublime Feathertouch as I have, attaching the finder to the scope presents a bit of a challenge. The finder bracket is easily attached to a mounting plate located on the stock focuser, but no such provision exists on the Feathertouch. Fortunately, there is a rather simple solution. The bracket is attached a 76mn tube-ring which snuggly fits the outside diameter of the focuser. This comfortably holds the finder in place and can be adjusted by simply loosening and tightening the thumb screw on the tube ring.

The 76mm tube-ring fits perfectly around the Feathertouch focuser.

Under the Night Sky
First light with the FC-76 came almost a year after I purchased both the FS-60 and Objective Unit having somewhat fallen in love with the baby Tak on a trip to Namibia. However more local dark skies beckoned and not wanting to carry one of larger LZOS made triplets, the FC-76 suddenly seemed like the perfect choice. Those first views of some showpiece DSOs of the Northern Hemisphere were impressive to say the least.

The star test is among the very best I have seen. The Fresnel diffraction pattern showing virtually perfect levels of spherical correction, with a pale green rim outside of focus and a delicate magenta hue inside.

The view in the eyepiece is the classic razor-sharp tiny jewels on jet black cloth that no other telescope design seems to be able to quite match. As with all quality telescopes, the image snaps to focus. At f/7.5, the focal ratio is slightly longer than I am used to with all my other refractors and the small increase in the depth of field is welcome, requiring less frequent focusing due to atmospheric induced focus issues. Inspection of the summer Milky Way star clouds with a widefield eyepiece showed an image which is sharp over 90-95% of the field with a slight defocusing due to field curvature at the very edge of the field.

The FC-76 DCU set up for a night of stargazing at Astrocamp in the Brecon Beacons.

When it comes to refractors, questions inevitably turn to false colour (personally I would be more worried about spherical aberration) and here the FC-76 does exceptionally well. While it is not quite in the same league as my LZOS triplets which are completely colour free, the FC-76 shows no extraneous colour at all on all but the most challenging of objects. I have been unable to detect any false colour on the Moon or Jupiter even at magnifications approaching 200 times. However, Venus and some particularly bright stars such as Sirius do show some very minor colour fringing but I would highlight that I really had to look for it and in no way detracts from the sharp, high contrast views.

Many astronomers believe that a 4” scope is the minimum aperture needed for serious planetary observing but I would offer the FC-76 as evidence to the contrary. Just like its little brother, the FS-60, the lack of scatter around bright planets and the limb of the moon is remarkable, and this improved contrast really brings subtle planetary detail into view. Jupiter shows a wealth of detail including several bands, dark storms and incredibly a salmon pink colour (using the Baader BBHS diagonal) in the GRS. I have heard it said that 6” in the minimum aperture for colour to be seen in the GRS. Transits of the Galilean moons and their shadows are easy.

Mars is the Achilles heel of the basic FS-60. Not so with the FC-76. Though the recent opposition was not particularly favourable from the UK, at times of good seeing I was rather surprised by just how many surface features I was able to see. Saturn is similarly impressive with the subtle banding immediately obvious.

While I am not a huge fan of lunar observation, the views are outstanding. Shadows are jet black, and the whites are as pure as snow. The lack of scatter really reveals itself on the limb where the sky is pure black. On bright objects like the moon, the ability to really take the magnification up demonstrates the quality of the lens. Even using the 2mm setting on my 2-4mm Nagler Zoom for 285x reveals a super sharp image, even if the view reveals no additional detail and the exit pupil is risking floaters in the observer’s eye ruining the view.

All the usual suspects in the double star world are easy quarry for the FC-76, such as Castor, the Double-Double and Polaris (usually considered a decent test for a 3” scope), more often than not at relatively low magnification. That performance is hardly surprising given the quality of the star test and sharpness of the image seen in the eyepiece. In an effort to discover just what this scope is capable of, I have run the gauntlet of increasingly challenging doubles, and the FC-76 has left me more than impressed. Propus in Gemini is listed in Burnham’s as a challenge for a 12” scope (that is perhaps a bit pessimistic and might be more reflective of the general quality of telescope objectives when published though the components were also slightly tighter at the time of writing). I have certainly seen 8” scopes fail to show the fainter secondary on nights of less than perfect seeing. In my attempt to split this double (1.6” separation / magnitude 3.29 & 6.15) I actually removed the diagonal and used straight through viewing (not friendly on the neck) to reduce the already low scatter still further and keep optical components in the light path to a minimum. On one night of exceptional seeing, I was able to glimpse the tiny secondary at 190x (3mm setting of Nagler Zoom), like a small pimple on the edge of the bright primary. That is an exceptional result.

The E and F components of the Trapezium in M42 can be tricky for a scope of even quite large aperture when seeing conditions are poor. However, it can be an excellent test of optical quality in small scopes (4” class and under) when seeing is very good. A small scope with more than a modest amount of spherical aberration will reduce contrast and slightly smear the image rendering those elusive fainter components of the most famous multiple star system invisible against the bright nebula that cradles them. Using the 4mm setting of my Nagler Zoom (143x), I have been able to pull E consistently and F intermittently on nights of good seeing, providing further evidence of what the star test showed, that my FC-76 has exceptional optics. It is certainly the smallest scope I have used that has achieved this, though I am not alone in this feat with a couple of other owners of 3” class scopes reporting success online. However there are many, many more reports of similar aperture, and larger scopes, failing to achieve this.

Combined with suitable solar observing safety equipment such as the Baader Herschel Wedge seen here, the FC-76 is a very capable instrument for studying our nearest star.

When it comes to deep sky I would suggest that the scope punches above its weight, especially from a dark sky site, thanks to the exceptional sharpness and contrast of the views provided. My experience with the FC-76 has led me to conclude that it matches lower quality scopes that boast an inch or more of additional aperture in the detail that can been seen even if the image itself is a touch darker than those larger scopes thanks to excellent contrast. During the autumn 2016 Astro Camp, one of the organisers came up to me on the observing field for a chat when I was pointing the scope at M13 in Hercules. Being a silver rated International Dark Sky Association reserve, it was rather dark which meant it was quite difficult to identify what scope I was observing with. I offered a look and he was immediately impressed with the image seen, saying the cluster was resolving nicely towards the core. I retorted that it was “not bad for a 3-inch scope” which immediately generated a “that’s only a 3-inch?!” response followed by an immediate return to the eyepiece for another look. The next statement summed up my opinion of this remarkable little scope. “That is a very sharp image, those optics are very good.” Agreeing, I then slewed the scope to the Double Cluster in Perseus which generated a similar positive response. Such an assessment from another experienced astronomer only further reinforces the conclusion that I have reached over the last couple of years of ownership.

Another FC-76
It should be clear by this stage of the review that I am rather impressed with the quality of the FC-76 but one exceptional model is no guarantee (despite Takahashi’s reputation) that all examples are of a similarly high standard. While only one additional scope is not a sample set to draw any definitive conclusions, I was fortunate enough to spend some time with another astronomer’s FC-76DS under the dark skies of the Brecon Beacons and found the view through his scope to be equally as impressive. While we did not test the scope rigorously, it was clear from the views presented that this scope was of a similarly high quality to my own FC-76.

Travelling with the FC-76
With no component of the telescope more than 13.5” in length, it is possible to pack this down into a bag which will comply with the most restrictive of cabin baggage allowances. I use the Think Tank Photo Airport Essentials backpack (you can read the review of the Essentials Backpack here) which is so small that it actually fits under the seat in front of you a plane, should the need arise. The accompanying photograph shows how much equipment I am packing for my summer 2017 trip to Vamizi island off the cost of Mozambique.

The FC-76 and all required accessories along with plenty of camera equipment fit in the Think Tank Photo camera bag.

To keep weight down I use a 1.25” diagonal (with extension tube) and take three eyepieces, a 24mm Panoptic (24x/2.7o field), a 7mm Nagler Type 6 (81x/0.98o) and a 3-6mm Nagler Zoom (95x-190x/0.51o-0.26o). All three eyepieces are high quality and provide me the max field of view possible from a 1.25” EP through to very usable magnifications for planetary and double star work.

Takahashi FC-76 DCU + EX-CQ
Google translating some Japanese websites suggests the 1.7x CQ module that converts the FS-60 into the f/10 quadruplet FS-60Q can also be used with the FC-76 objective unit to create an f/12.6 quadruplet. This is perhaps a little surprising as I was under the impression that the CQ unit was specifically designed for the FS-60. However, confirmation that this could be done came in May 2016 when Takahashi produced a limited run of 30 FC-76 DCU + EX-CQ packages which included the Objective Unit, the Focuser Unit and CQ Module all in a travel bag. Using the slightly unsafe method of Google translate on Japanese websites (it translates Fluorite as Flow-Light thanks to phonetic translation) reveals a claim that use of the CQ module improves the polychromatic strehl ratio to almost 0.95, an incredibly high value for any telescope. I do own the CQ module, but have yet to try this but certainly will soon.

This will be exciting to try! The FC-76 objective unit, the 1.7x CQ module and focusing unit. Combined they create a 3″ f/12.6 scope.

Conclusion
The Takahashi FC-76 lens is exceptional. The lack of scatter, extreme contrast and excellent sharpness allow it to perform at levels above what would be expected of a 3” telescope. All of the FC-76 models are portable, quick to deliver maximum performance when taken outside from a warm house, and can take high levels of magnification allowing them to deliver on planets and double star work.

Would I recommend this scope to a beginner? No, certainly not. It is expensive and you would get a lot more bang for your buck with a 6 or 8” Newtonian. But if you are an experienced astronomer looking for an ultra-portable scope to take away to distant lands with dark skies and you demand optics that are among the very best available, the FC-76 Objective Unit is highly recommended, either to those who already own the baby Tak (FS-60) or to those who are prepared to construct it themselves (hopefully Takahashi bring the FC-76 DCU to the West so you won’t have to) as mentioned earlier in the review.